Investigation of electrostriction appliance and its applicationfor bionics flapping aircraft

A novel design for an electrostriction appliance derived from the theory and application of electromagnetics is presented. The working principle, that is the application of gravitation and elasticity together to realize the ＂shrinking＂ and ＂extending＂ effect from the distortion and transforming power into mechanical energy, is briefly explained. The characteristic parameter relationships are established and the experimental research is performed. Experimental results show that this sort of electrostriction appliance can perform well as regards driving force and beeline displacement, and furthermore, its self-weight is smaller. This makes it suitable for beeline drivers with a high application value, especially for the driver of the bionic appliance. In the application of the electrostriction appliance to a bionics-flapping aircraft, the wings can work with a flapping angle in the range of a certain value by controlling the ＂shrinking＂ and ＂extending＂ of the electrostriction appliance. It can reduce the startup power and the impact load of the driver. The flapping extent of the wings will change when the voltage which is put into the electrostriction appliance varies. This makes it more flexible as the bionics-flapping aircraft realizes different actions of flying.

Preparation and electrostriction of BaTiO_3/polyurethane nanocomposite elastomers

BaTiO3/polyurethane （BaTiO3/PU） nanocomposite elastomers were prepared from barium titanate nanoparticles, polyester polyol, 2, 4-toluene diisocyanate, 1,4-butanediol and 1, 1, 1-trimethanol propane by the one-step method. The density, hardness and dielectric constant of BaTiO3/PU nanocomposite elastomers increased with the increase of the content of BaTiO3 nanoparticles in nanocomposites. The electrostrictive properties of BaTiO3/PU nanocomposite elastomers were investigated by the digital speckle correlation method （DSCM）. It was found that through the on-and-off of the electric field, the electrostrictive strains of BaTiO3/PU nanocomposite elastomers revealed corresponding shrinkage and recovery. The electrostrictive coefficient of BaTiO3/PU nanocomposite elastomers was greater than that of the corresponding polyurethane elastomers, and the electrostrictive coefficient of composites decreased with the increase of the content of barium titanate nanoparticles.

Nonlinear dynamic analysis of dielectric elastomer membrane with electrostriction

The dielectric elastomer(DE)is an important intelligent soft material widely used in soft actuators,and the dynamic response of the DE is highly nonlinear due to the material properties.In the DE,electrostriction denotes the deformation-dependent permittivity.In the present study,we formulate the nonlinear dynamic governing equations of the DE membrane considering the electrostriction effect.The free vibration and parametric excitation of the DE membrane with different geometric sizes are calculated.The free vibration bifurcations induced by the initial location and the voltage are both discussed according to an energy-based approach.The amplitude-frequency characteristics and bifurcation diagrams of parametric excitation are also given.The results show that electrostriction decreases the free vibration amplitude and increases the frequency,but it has less influence on the parametric excitation oscillation frequency and decreases the parametric excitation amplitude except when the membrane resonates.The initial location and the applied voltage can induce the snap-through instability of the free vibration.A large geometric size will lead to a much lower resonance frequency.The resonance amplitudes increase while the resonance frequencies decrease with the increase in the applied voltage.The critical voltage of snap-through instability for the parametric excitation is larger than that for the free vibration one.

The Study of Optoacoustic First and Second Sound Waves in Superfluid Helium under the Effect of Gaussian Laser Light Considering Electrostriction Mechanism

The present paper is aimed to study the effect of Gaussian laser light on first and second sound waves in superfluid helium theoretically using optoacoustic method. The mechanism applied in this study is electrostriction mechanism. This study considers crystal parts of superfluid helium with a zero absorption coefficient applying electrostriction mechanism. Affecting Gaussian laser light on these crystal parts, a spectrum of cylindrical first and second sound waves and cylindrical slow and rapid waves is obtained. Meanwhile, frequency of waves amplitudes proportionate to time period of laser light is calculated.

Surface Tension and Electrostriction in a Suspended Bridge of Dielectric Liquid

The mechanism of the formation of a surprisingly long suspended liquid bridge subjected to a dc electric field has been intensively studied in the past few decades. However, the role of electrostriction and quantitative evaluation of surface tension in the bridge have not been evaluated. We present combined theoretical and experimental studies on this issue. Electrostriction is pointed out to be the driving force that pushes liquid upward against gravity and into the gap between two containers and forms the suspended bridge, which is within the framework of the Maxwell pressure tensor. Through a comparison between experiment and theory, the surface tension is found to play an important role in holding the long suspended bridge. Ignorance of the surface tension leads to much smaller bridge length than the experimental values. The dynamic stability of the bridge with respect to its diameter, length and conductance is also discussed.

New method for measuring high field electrostrictive response of barium titanate/polyurethane elastomer

A new method for measuring the characteristic of electrostriction by a digital speckle correlation method （DSCM） is presented. The in-plane displacement is obtained by using the DSCM, and the out-plane displacement is obtained by the geometrical relation of the triangle theory. In this application, high field electrostrictive strains of barium titanate/polyurethane elastomer composite materials are measured. The electrostrictive strain is evaluated when the application of an electric field is repeated, and then the electrostrictive coefficient of the sample is obtained. To improve the measuring accuracy, the bilinear interpolation of gray value is used to obtain the sub-pixel gray value. The results are compared with those obtained from the surface fitting algorithm. The experimental results demonstrate that the electrostrictive response of polyurethane increases with the introduction of barium titanate into polyurethane. And by using the DSCM, the measurement of the characteristic of electrostriction can be done quickly and accurately. The DSCM provides an effective tool for the evaluation of electrostrictive response.

Characteristic of Intelligent Air Bag Venting Structure Actuating by Electrostrictive Stack Actuator

In this paper the conception of smart materials and structures is firstly combined with research of air bag,and the main theory of self adapting cushioning of intelligent air bag is expatiated.The intelligent venting structure is the main part affecting the cushioning result.Electrostrictive material was found having big force,high response speed and wide linearity,and it is fit to utilize in intelligent venting structure. The characteristic of the dynamic response and cushioning actuating of an electrostrictive stack actuator is analyzed,and the result of the computer simulation of the fuzzy control to intelligent venting structure is given.It is concluded that intelligent venting structure has good actuating characteristic and can satisfy the need of intelligent air bag.

SOME PROBLEMS IN ELECTROSTRICTIVE AND MAGNETOSTRICTIVE MATERIALS

Some of the previous theories in the electrostrictive and magnetostrictive materials and their differences are discussed in this paper. A variational principle in the general thermodynamic sense is given and the governing equations can be derived from this principle. Illustrational examples are given.

Coupled FEM Analyses on Electro-mechanical Problem of Electrostrictive Plate with Elliptical Hole

A detailed theoretical construction of general coupled 3DFEM analyses of anisotropic dielectrics is first presented by considering the electric body force and body couple moment.A 3Delectrostrictive element is subsequently defined in ABAQUS user subroutine UEL and the post-processing of finite element method(FEM)results is realized by UVARM and dummy element method.Then the developed technique is used to solve the electro-elastic field of an isotropic electrostrictive plate with an elliptical hole subjected to electrical load.By comparing the coupled and uncoupled numerical results,the traditional uncoupled analytical method can cause a large error when the applied electric field or the electrostrictive performance of the dielectric is high,and thus the present coupled analysis is especially necessary.

Control model for experiments on piezoelectric and electrostrictive elements

As an ideal micro displacement actuator, piezoelectric and electrostrictive elements are in wide use in many fields, but their further application is restricted because of its shortages such as hysteresis, creep and non linearity. Through the analysis of the polarization mechanism of piezoelectric and electrostrictive elements, a new normalization model was proposed, analysis and experiments are run with the model, and the linearity of voltage displacement curve is analyzed as well.

WAVE PROPAGATION IN ELECTROSTRICTIVE MATERIALS UNDER BIASED FIELDS

Constitutive relations for nonlinear, isotropic, electroelastic solids quadratic in the ?nite strain tensor and the referential electric ?eld are derived from the full nonlinearity theory of electroelasticity by tensor invariants, which can describe the behavior of electrostrictive ma- terials. The equations are linearized for small, dynamic ?elds superposed on ?nite, static biased ?elds. These linear equations are used to study plane waves propagating in an electroelastic body under various mechanical and/or electric biased ?elds. It is shown that the speed of the acoustic waves exhibits a strong dependence upon those material parameters in the nonlinear constitu- tive relations. Experimental determination of these material parameters using this dependence is discussed.

ANALYSIS OF AN ELECTROSTRICTIVE STACK ACTUATOR FOR ACTIVE TRAILING EDGE FLAPS

Stack actuator is a solid-state driving component of Active Tailing Edge Flap in smart rotor systems. It is a multi-layer serial structure of basic units composed of electrostrictive and adhesive layers. In this paper, a dynamic model of the actuator is derived based on the constitutive equation of electrostrictive material and the equation of motion. Theoretical analysis is made on the factors involved in the design of the actuator, which reveals that the electrostrictive layer and the adhesive layer should be optimized to compromise between displacement and frequency requirements. In the final part of the paper, the experiment of an ATEF system is introduced. The results show that the model is reasonable. It also suggests that the bending stiffness of elastic mechanism is an important factor in design, which should be carefully studied to provide satisfactory dynamic response of the ATEF system.

The Experimental Study of Micro-Tool Servo with Electrostrictive Actuator

An experimental study of micro-tool servo with electrostrictive actuator is presented.The design methods as well as the performance of the entire mechanism is given out.The results of the experiment show that the resolution of the micro-tool servo is 0.02μm and the frequency response is up to 200Hz,which satisfies the requirements of the ultra-precision machining.

电致伸缩效应下水中电子输运特性

水中快脉冲(脉宽数ns甚至ps级)放电过程中,快脉冲在电极附近引起电致伸缩效应导致电极附近形成空化区.电子在空化区内积累能量并高速进入水体,电子在水中的输运特性是水中脉冲放电起始与发展的关键因素.本文构建了考虑弹性与非弹性碰撞截面的水中电子输运物理模型,采用蒙特卡罗方法研究不同能量电子的透射与散射径迹结构特征,研究了弹性碰撞、电离与激发碰撞频次随电子初始能量的变化以及水中电子能量损失特征.结果表明,较低能量的电子(约20 eV)受水分子散射影响能量损失较大,透射能力较弱,随着电子初始能量的增高,电子受水分子散射作用的影响逐渐减小,具有更强的液体穿透能力;弹性碰撞次数远大于激发与电离碰撞,导致电子散射距离与透射深度相当,电离碰撞和激发碰撞次数随电子能量升高显著增加;电子入射能量越高,其能损越大,随运动距离增加,能损急剧下降,与电子的平均电离能量损失W变化趋势一致.本研究可为探究快脉冲放电机理提供重要数据基础.

浅析电介质的极化——从物理竞赛题到几何相位

在电磁学和电动力学教学内容中,介质的极化是非常重要的组成部分。为了给学生们解释极化的微观机制,教材通常采用了洛伦兹模型的物理图像。该物理图像清晰简单,有利于初学者快速理解极化的物理本质。但洛伦兹模型却存在一定程度的不自洽性。此外,使用洛伦兹模型解决物理竞赛题时,也出现了悖论。本文中,我们首先回顾物理竞赛题目中的这个经典悖论,然后介绍了介质极化矢量更严格的定义,描述了介质极化过程中发生的微观物理过程,并在此基础上用热力学解释了悖论出现的原因和解决方法,最后简单介绍了计算介质极化的几何相位理论。

A Novel Capacitive Pressure Sensor

A novel capacitive pressure sensor is presented, whose sensing structure is a solid-state capacitor consisting of three square membranes with Al/SiO2/n-type silicon. It was fabricated using pn junction self-stop etching combined with adhesive bonding,and only three masks were used during the process. Sensors with side lengths of 1000,1200,and 1400μm were fabricated,showing sensitivity of 1.8,2.3, and 3.6fF/hPa over the range of 410～ 1010hPa, respectively. The sensi- tivity of the sensor with a side length of 1500μm is 4. 6fF/hPa,the nonlinearity is 6. 4% ,and the max hysteresis is 3.6%. The results show that permittivity change plays an important part in the capacitance change.

弛豫型铁电体PZNT制备与性能研究的进展

本文综述了近年来国际上弛豫型铁电体PZNT的制备与介电、压电及电致伸缩性能研究的进展．PZNT单晶体的制备方法以高温PbO熔剂法为主，其尺寸已达40mm．随PT含量的变化，PZNT的顺电一铁电相交由弥散性、混合型变为一级相变；其铁电-铁电相变可由组份或电场诱导，由介电性能表征．压电性能在MPB处及偏向三方相一侧达到最佳，＜001＞切向的三方相与四方相单晶可分别作为频带宽、分辨率高、且阻抗匹配好的新一代声阵列与单个器件传感器．＜001＞向的PZNT单晶具有巨大的电致伸缩应变，可望成为高性能的固体驱动器．

微小型微步距进给驱动装置及其应用研究

研制成两类任意行程、微步距进给驱动装置。设计并组建了与之配套的驱动控制源和相应的检测系统、便携式电加工系统、放电检测和系统性能测试环节；

两种压电陶瓷微位移器的特性分析与实验对比

压电和电致伸缩材料，根据其压电和电致伸缩效应，可作为新型的微位移器件。它具有结构紧凑、体积小、分辨率高、控制简单等优点。不存在发热问题，容易实现０．０１μｍ的位移精度。在精密机械及航空航天精密工艺中得到了广泛应用。本文对这两种材料的机电耦合效应进行了描述。并通过实验曲线对两种典型的压电和电致伸缩材料的特性进行了分析对比，指出了各自的适用范围。

压电/电致伸缩材料及驱动器的新技术与应用

压电 /电致伸缩驱动器是一种广泛使用的驱动器 ,文章概括总结了几种压电 /电致伸缩新材料的发展方向 ,同时还介绍了几种新型驱动模式和超声电机的研究动态 ,并对压电 /电致伸缩驱动器的发展前景予以展望。